Chancellor George Osborne also welcomed Google's further investment in the area, describing it as "great news".
"It shows that we can create the right environment to attract start-ups and established high-technology businesses," he said. "This shows that Britain is open for high-tech business."
Yammer European head, Mike Grafham, told V3 he was pleased Google was expanding its presence in the area, where Yammer recently set up its own European base.
"I think this is great news and another huge boost for the area. It's only going to increase the attraction of talent to Tech City, and will also obviously drive further development; so it's likely that everyone here is going to benefit," he said.
Huddle chief executive, Alastair Mitchell, further welcomed the news, but said Google moving to the area is "just the beginning".
He said that in order to create a true Tech City, you do not just need new innovation hubs and massive investment, but also networks and ecosystems.
"The new tech kids on the block, or the roundabout, will gain a new place to congregate, work and share ideas. The whole area will also benefit from the visibility of a tech goliath setting up shop here and more talent will head to Old Street," Mitchell told V3.
"However really, the seven story hub is just the foundation for what we really need - an effective, organic entrepreneur ecosystem. We need to make sure that the Tech City isn't just a wealth of new buildings and high speed internet, but an environment where second and third time entrepreneurs support, advise and invest in the new breed of start-ups."
Google's announcement follows similar moves by O2, which opened a workspace in Tottenham Court Road last week designed for start-ups and flexible workers.
The workspace can cater for up to 75 people, and contains open workstations that provide access to power and wireless printers for 10 people at a time.
In related news, today is the six-month anniversary of Startup Britain, an initiative established in March to encourage the UK's most successful entrepreneurs and businesses to provide support to start-ups.
Barclays, Microsoft and Virgin Media are some of the companies backing the venture.
"Engaged with over 160k people so far and still lots to do!" said Startup Britain in a tweet.
City of Glasgow College teams up with NetApp
Have we found some cracking deals for you!
The best Black Friday deals on smart home devices
Intel plans to halt support for BIOS